RO 4x150gpd membrane fixed-but I have no idea why this happened.

Hi everyone,
Just thought I would post this as I really don't understand what happened completely-just guesses...
My RO system was only taking sap up 1% (3 to 4)... 4 membranes in series with 8800 pump.
Setup was in series, but the pressure/flow just wasn't right. My pressure gauge is 50psi by default now. I tried to neutralize it but didn't work so needle is way off.
I took it apart and out of frustration just tossed all the membranes in water. Eventually they sank and I thought -now that's weird. So I put one membrane in and it worked upping my sap 2.5%.
Well, okay... let's put 1 in parallel...that worked well too.
So then I thought okay, let's put the other 2 in series... well dang man... 3x the volume and it upped my brix to +6 sometimes 7.
Sinking the membranes did something. Not sure exactly what, but it worked.
If someone out there can explain this please do.